Unit 5 Evolution

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Unit 5 Evolution

• Ch. 17 The History of Life

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Fossils Ancient Life

• Paleontologists - scientists that study fossils
• From fossils, scientists can infer what past life
  forms were like their structure, what they ate,
  what ate them, the environ. where
  they lived

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Fossils Ancient Life

• They group similar organisms together arrange
  them in the order that they lived, from oldest to
  most recent
• Together, all this info. about past life is
  called the fossil record

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Fossils Ancient Life

• The fossil record provides evidence about the
  history of life on Earth
• It also shows how different groups of organisms,
  including species, have changed over time

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Fossils Ancient Life

• The fossil record shows that more than 99 of all
  species that have ever lived on Earth have become
  extinct
• Extinct - the species died out

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Interpreting Fossil Evidence

• Relative dating - determining the age of a fossil
  by comparing its placement with that of fossils
  in other layers

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Interpreting Fossil Evidence

• Scientists use radioactive decay to assign
  absolute ages to rocks.
• Radioactive elements decay or breakdown at a
  steady rate which is called its half-life.

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Formation of Earth

• Earths early atmosphere probably contained
  hydrogen cyanide, carbon dioxide, carbon
  monoxide, nitrogen, hydrogen sulfide, water

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Figure 17-8 Miller-Urey Experiment
Secion 17-2
Mixture of gases simulating atmospheres of early
Earth
Spark simulating lightning storms
Cold water cools chamber, causing droplets to form
Condensation chamber
Water vapor
Liquid containing amino acids and other organic
compounds
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Miller and Urey

• Miller and Ureys experiments suggested how
  mixtures of the organic compounds necessary for
  life could have arisen from simpler compounds
  present on a primative earth

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The First Organic Molecules

• Experiments have suggested how simple compounds
  found on the early Earth could have combined to
  form the organic compounds needed for life

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Free Oxygen

• The rise of oxygen in the atmosphere drove some
  life forms to extinction
• Others evolved new, more efficient metabolic
  pathways that used oxygen for respiration

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Origin of Eukaryotic Cells

• Endosymbiotic theory - proposes that eukaryotic
  cells arose from living communities formed by
  prokaryotic organisms

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Mass Extinction

• Mass extinction - when many types of living
  things become extinct at the same time
• At the end of the Paleozoic Era, a mass
  extinction affected both plants animals on land
  in the sea
• 95 of life in the oceans disappeared

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Patterns of Evolution

• Macroevolution - large-scale evolutionary
  patterns processes that occur over long periods
  of time
• 6 important topics in macroevolution are
• extinction
• adaptive radiation
• convergent evolution
• coevolution,
• punctuated equilibrium,
• changes in developmental genes

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Patterns of Evolution

• Extinction
• More than 99 of all species are now extinct
• It usually happens for a reason species compete
  for resources, environments change
• Some species adapt survive, others become
  extinct

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Patterns of Evolution

• Adaptive radiation - when a single species has
  evolved, through NS, into diverse forms that live
  in different ways
• Ex.) Darwins Finches

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Patterns of Evolution

• Convergent evolution - when unrelated organisms
  begin to resemble one another
• It has occurred in both plants animals
• Ex.) Swimming animals

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Patterns of Evolution

• Coevolution - when 2 species evolve in response
  to changes in each other over time
• Ex.) Orchid has long spur with nectar in its tip,
  a Hawk moth has equally long feeding tube that
  allows it to feed on the nectar

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Patterns of Evolution

• Punctuated equilibrium - a pattern of long,
  stable periods interrupted by brief periods of
  more rapid change